Editing Piccadilly line (section)

==Infrastructure==

===Signalling and electricity===
[[File:Lots.road.power.station.london.arp.jpg|thumb|[[Lots Road Power Station]], disused and planned to be redeveloped]]
The line from Cockfosters to Heathrow and South Harrow is controlled from a control centre at [[South Kensington tube station|South Kensington]],<ref name=isgaz1950signalpicc>{{cite news |url= https://www.islingtongazette.co.uk/news/piccadilly-line-trains-still-run-by-obsolete-signalling-system-from-the-1950s-1-5517895 |title=Piccadilly line trains still run by obsolete signalling system from the 1950s |work=Islington Gazette |date=15 May 2018 |last=Gelder |first=Sam |access-date=31 August 2020 |url-status=live |archive-date=31 August 2020 |archive-url= https://web.archive.org/web/20200831074109/https://www.islingtongazette.co.uk/news/piccadilly-line-trains-still-run-by-obsolete-signalling-system-from-the-1950s-1-5517895}}</ref> which replaced the old Earl's Court control centre, which was shared with the District line.<ref>{{cite web |last=Signalman |first=Llangollen |url= https://www.flickr.com/photos/llangollen_signalman/albums/72157637392832414 |title=Earls Court Control Room |publisher=Flickr |date=6 November 2013 |access-date=14 July 2017}}</ref> Rayners Lane signal cabin is responsible for signalling the Piccadilly line from just northwest of South Harrow to Uxbridge, as well as the Metropolitan line joining at Rayners Lane.<ref>{{cite web|last=Signalman |first=Llangollen |url=https://www.flickr.com/photos/llangollen_signalman/albums/72157657032080114 |title=Rayners Lane |publisher=Flickr |date=1 October 2015 |access-date=14 July 2017}}</ref> The signalling system is expected to be upgraded in line with the Deep Tube upgrade, which will increase line frequencies up to 33 tph.<ref name=isgaz1950signalpicc/> Trains may also be able to make a permanent additional stop at Turnham Green following this upgrade.<ref>{{cite news |url= https://www.guardian-series.co.uk/news/18213985.tfl-says-piccadilly-tube-upgrade-number-one-priority/ |title=TfL says Piccadilly Tube upgrade is "number one priority" |date=6 February 2020 |access-date=31 August 2020 |last=Mathewson |first=Jessie |work=East London & West Essex Guardian |url-status=live |archive-date=31 August 2020 |archive-url= https://web.archive.org/web/20200831075525/https://www.guardian-series.co.uk/news/18213985.tfl-says-piccadilly-tube-upgrade-number-one-priority/ }}</ref>

When the line was opened from Finsbury Park to Hammersmith, its [[signalling]] system was identical to the Bakerloo and District lines. Small cabins at each location of crossover installed controlled the signals there. Single lamps displayed track clearance in the form of green or red, with variations of yellow at difficult-to-spot locations. This equipment was supplied by [[Westinghouse Rail Systems|Westinghouse]] and operated using compressed air. The exception was between West Kensington and Hammersmith, where it was controlled by District Railway signal boxes, and had semaphore signals instead.{{sfn|Horne|2007|p=27}}{{sfn|Horne|2006|pp=37–40}} The Piccadilly line extensions resulted in resignalling on tracks west of Barons Court. Signal cabins were adjusted and new ones were added at Hammersmith, Acton Town and Northfields. A mixture of [[Railway semaphore signal|semaphore]] and colour-light signals were used on the four-track section. Signalling was redone on the new Uxbridge branch.{{sfn|Horne|2007|p=57}}{{refn|Most of the existing semaphore signals on the District line branch to South Harrow were replaced with coloured light signals between October and December 1932.{{sfn|Horne|2007|p=57}}|group=note}}

Speed control was introduced at several stations to enhance the signalling system after World War II. This enabled a train to proceed slowly into an occupied platform without stopping in front of another before it departed, thus improving headways. The last semaphore signal, at [[Ealing Common tube station|Ealing Common]], was replaced in November 1953.{{sfn|Horne|2007|p=128}} A control room was built at Earl's Court to centralise supervision of most of the line signalling in the 1960s, while Rayners Lane signal cabin was, and still is, the main control centre of the Rayners Lane to Uxbridge portion;{{sfn|Horne|2007|p=126}} shared with the Metropolitan line.<ref name=cartomap /> 1930s automatic signalling equipment was updated in the 1970s and 1980s.{{sfn|Horne|2007|p=127}}

The UERL built a large power station that would be capable of providing power for the District line and the underground lines planned. Work began in 1902 at Lots Road, by [[Counter's Creek|Chelsea Creek]], and in February 1905 Lots Road Power Station began generating electricity at {{nowrap|{{val|11|u=kV}} {{Fraction|33|1|3}} Hz}}, conveyed by high-voltage cables to substations that converted this to approximately {{val|550|u=V|s=&nbsp;DC}}.{{sfn|Horne|2006|p=40}} On the Piccadilly line, electricity was transmitted via underground ducts to Earl's Court, which was then distributed to different substations.{{sfn|Horne|2007|p=27}}{{refn|Direct traction current was also provided from District line substations at Earl's Court and South Kensington.{{sfn|Horne|2007|p=27}}|group=note}} Power supply for the Cockfosters extension was initially generated by the North Metropolitan Electric Power Supply Company at Wood Green.{{sfn|Horne|2007|pp=78–81}} It was later supplied by Lots Road station. The [[National Grid (Great Britain)|National Grid network]] took over the supply on the Ravenscourt Park to Uxbridge and Northfields section. Lots Road was permanently closed on 31 October 2003, being also replaced by power supply from the National Grid Network. Emergency lighting, powered by batteries, is available at every station, with emergency supply from a support power station in [[Greenwich]].{{sfn|Horne|2007|p=127}}

===Depots and sidings===
[[File:Northfields Depot (18036366511).jpg|thumb|Northfields Depot, with an [[London Underground S7 and S8 Stock|S stock]] train]]
The line has two depots, at [[Cockfosters tube station|Cockfosters]] and [[Northfields Depot|Northfields]]. The former site is near [[Trent Park]], and was the preferred site over [[Oakwood tube station|Oakwood]], which was smaller,{{sfn|Horne|2007|p=66}} and its only access point was south of the station. Subsequently, Oakwood was built with an island platform, with its intended three-track terminus layout moved to Cockfosters.{{sfn|Horne|2007|p=72}} Light maintenance and cleaning of trains is done here, with the latter site, being the main depot, having train maintenance facilities.{{sfn|Horne|2007|p=127}} Northfields depot is also double-ended, with access from just west of [[Boston Manor tube station|Boston Manor station]]{{sfn|Horne|2007|p=50}} and Northfields station. For it to be built, the latter station had to be rebuilt nearer to [[South Ealing tube station|South Ealing station]].{{sfn|Horne|2007|p=55}} The depot was opened earlier than the Hounslow extension, on 4 July 1932, and fully electrified two months later.{{sfn|Horne|2007|p=57}}<ref name=cartomap/>{{refn|When opened, some District line trains were stabled here.{{sfn|Horne|2007|p=57}}|group=note}}

Single [[Siding (rail)|sidings]] are placed at Rayners Lane, Oakwood, Down Street (Hyde Park Corner), and Wood Green. Arnos Grove, Acton Town, South Harrow, Uxbridge, Hammersmith and Heathrow Terminal 5 have more than one siding for reversing trains or storing them.<ref name=cartomap/> Four [[Crossover (rail)|crossovers]] were built for the initial line opening in 1906,{{sfn|Horne|2007|p=27}} [[Hounslow Central tube station|Hounslow Central]] on 3 March 1923,{{sfn|Horne|2007|p=46}} and double crossovers at South Harrow were added in the 1930s.{{sfn|Horne|2007|p=57}}

Crossovers with other lines are present on the Piccadilly line. A connecting tunnel from the northbound Piccadilly line at King's Cross St Pancras to the northbound [[Northern line]] Bank branch was constructed in 1927.{{sfn|Horne|2007|p=98}}{{refn|It was built to facilitate rolling stock transfers between lines and to reach [[Acton depot|Acton works]].{{sfn|Horne|2007|p=98}}|group=note}} At Finsbury Park, a set of crossovers in the south were retained where trains can cross over onto the Victoria line.{{sfn|Horne|2007|p=114}}

[[Lillie Bridge Depot|Lillie Bridge]] was the main depot when the Piccadilly line was initially opened. Trains entering service on the line had to reverse and enter the District line tracks first via [[West Kensington tube station|West Kensington]].{{sfn|Horne|2007|p=26}}{{sfn|Follenfant|1974|p=130}} When the Piccadilly and District line tracks were realigned in the 1930s, access points into the depot had to be altered.{{sfn|Horne|2007|p=54}}{{sfn|Follenfant|1974|p=131}} When the line was extended to Northfields and Cockfosters in 1933, all trains except seven{{refn|This figure excluded trains serving the Aldwych branch which were also parked at the depot.{{sfn|Horne|2007|p=57}}|group=note}} were stabled at the newer depot.{{sfn|Horne|2007|p=57}} Once the Cockfosters depot was opened, Lillie Bridge was converted to a maintenance depot, where it housed only engineers' and materials trains.{{sfn|Horne|2007|p=90}}{{sfn|Follenfant|1974|p=130}}

===Station lifts and escalators===
Most original deep-level stations were installed with lifts and stairs, with some descending directly down to platform level.{{sfn|Wolmar|2005|p=188}} Many of these were given an overhaul in the 1930s with escalators replacing lifts for quicker passenger flow.{{sfn|Badsey-Ellis|2016|p=212}}{{sfn|Horne|2007|p=93}} Underground stations on the Cockfosters extension were built with access mainly via escalators; each station shaft are able to fit three escalators, but some stations had two escalators with a stairwell by the middle. Escalators at Bounds Green, Wood Green and Manor House travel at {{convert|165|ft|m}} per minute, which were then the quickest on the network.{{sfn|Horne|2007|p=82}} All of the original lifts were either replaced by new equipment or were converted to escalators. [[Alperton tube station|Alperton]] was the only above ground station to have an escalator, which was transferred over from the [[Festival of Britain]], but was decommissioned in 1988.{{sfn|Horne|2007|p=128}} Stations such as Green Park and King's Cross St Pancras were installed with new lifts to provide step-free access to every platform by the [[2012 Summer Olympics]].<ref name="upgrade2008">{{cite press release |url=https://tfl.gov.uk/info-for/media/press-releases/2008/august/green-park-tube-station-to-be-upgraded-ahead-of-london-2012-games |title=Green Park Tube station to be upgraded ahead of London 2012 Games |publisher=[[Transport for London]] |date=18 August 2008 |access-date=30 August 2020 |url-status=live |archive-date=30 August 2020 |archive-url=https://web.archive.org/web/20200830162224/https://tfl.gov.uk/info-for/media/press-releases/2008/august/green-park-tube-station-to-be-upgraded-ahead-of-london-2012-games }}</ref><ref name="upgrade2011">{{cite press release |url=https://tfl.gov.uk/info-for/media/press-releases/2011/september/transformation-of-green-park-station-nears-completion |title=Transformation of Green Park station nears completion |publisher=[[Transport for London]] |date=6 September 2011 |access-date=30 August 2020 |url-status=live |archive-date=30 August 2020 |archive-url=https://web.archive.org/web/20200830162224/https://tfl.gov.uk/info-for/media/press-releases/2008/august/green-park-tube-station-to-be-upgraded-ahead-of-london-2012-games}}</ref><ref>{{Cite magazine |last=Cole |first=Margo |date=22 April 2010 |title=Major Project – King's Cross Underground Ticket Halls |url=http://leewoodprojects.co.uk/wp-content/uploads/2010/07/kings-cross-st-pancras-nce1.pdf |archive-url=https://web.archive.org/web/20170102152229/http://leewoodprojects.co.uk/wp-content/uploads/2010/07/kings-cross-st-pancras-nce1.pdf |archive-date=2017-01-02 |url-status=live |magazine=New Civil Engineer |pages=27–29 }}</ref><ref>{{cite press release |url=https://tfl.gov.uk/info-for/media/press-releases/2010/september/kings-cross-st-pancras-tube-station-is-stepfree-with-10-new-lifts |title=King's Cross St. Pancras Tube station is step-free with 10 new lifts |date=27 September 2010 |website=tfl.gov.uk |publisher=Transport for London|access-date=30 August 2020 |url-status=live |archive-date=30 August 2020 |archive-url=https://web.archive.org/web/20200830162625/https://tfl.gov.uk/info-for/media/press-releases/2010/september/kings-cross-st-pancras-tube-station-is-stepfree-with-10-new-lifts}}</ref>